1. Field of the Invention
The successful development of a vaccine against coccidia parasites requires obtaining parasite antigens that can block parasite invasion of host lymphocytes and prevent intracellular development or antigens that are sufficiently immunogenic in chickens to provide protection from infection. Identification of these antigens has been difficult to achieve, however, and the coccidia parasite antigens that interact with chicken lymphocytes have not previously been identified. Mouse monoclonal antibodies, although they have been available since 1985, are not effective for identifying coccidial antigens important in chickens since chickens recognize different antigenic determinants from mice. This invention relates to chicken hybridomas which secrete anti-coccidia monoclonal antibodies specific for antigens involved in parasite-host lymphocyte interactions. These antigens are important in the development of anti-coccidial vaccines as well as in the detection of coccidia parasites in infected animals.
2. Description of the Prior Art
Avian coccidiosis is caused by an intracellular protozoan parasite belonging to the genus Eimeria which infects the intestinal mucosa of livestock and poultry and seriously impairs the growth and feed utilization of the infected animals. The disease causes annual losses in the poultry industry of $440 million world wide. Identification of parasite antigens involved in the invasion of host lymphocytes is crucial for the development of coccidial vaccines, since sporozoite invasion of host lymphocytes is the first step involved in coccidiosis.
Mouse monoclonal antibodies (mAbs) have been used to characterize coccidial antigens (Danforth, H. D. 1983. Am. J. Vet. Res. vol. 44, pp. 1722-1727; Speer et al. 1983. J. Protozool. vol. 30, pp. 548-554) and to identify cDNAs encoding recombinant proteins of Eimerian parasites (Castel et al. 1991. J. Parasitol. vol. 77, pp. 384-390; Ko et al. 1990. Mol. Biochem. Parasitol. vol. 41, pp. 53-64). The use of these recombinant proteins as vaccines, however, has produced only limited success, and the use of mouse mAbs to define epitopes important in the chicken""s immune response to Eimeria is debatable since differences have been reported in the recognition of target antigens by immune sera from chickens, rabbits and mice (Jenkins and Dame. 1987. Mol. Biochem. Parasitol. vol. 25, pp. 155-164).
Nishinaka et al. (1991. J. Immunol. Methods. vol. 139, pp. 217-222, herein incorporated by reference) described a cell line for producing hybridomas from chicken cells, i.e. a chicken B cell line deficient in thymidine kinase activity fused with spleen cells of chickens immunized with keyhole limpet hemocyanin. The monoclonal antibodies produced by these cells, however, were suggested for use in clinical applications where the capability of avoiding reactivity with mammalian IgGs and activation of human complement systems would be important. There has been no suggestion of their use in elucidating immunological reactions in avian systems.
Thus, the need has continued for providing means for detecting and selecting for coccidia parasite antigens involved in the infection of host lymphocytes and capable of conferring protection against infection by Eimerian parasites.
We have discovered that monoclonal antibodies from chicken hybridomas are effective for identifying parasite antigens involved in the infection and invasion of host lymphocytes. In addition, these antigens are also useful for detecting the occurrence of parasite infection and for detecting the presence of parasites in a sample.
In accordance with this discovery, it is an object of the invention to provide a novel chicken monoclonal antibody which is specific for Eimeria antigens involved in host cell invasion and thus capable of detecting sporozoite antigens involved in host lymphocyte invasion.
It is also an object of the invention to provide a hybridoma cell line which produces the novel chicken monoclonal antibody.
Other objects and advantages of the invention will become readily apparent from the following description.